The Caldwells take a family trip to Puerto Rico where their father is also securing a secret business deal, while the kids find their own paths. Eight years have passed since the events of Au Pair, and newly graduated as his high school's valedictorian, Alexander Caldwell joins his visiting sister, college freshman Katie and her roommate Ariana on a family summer vacation with father Oliver and stepmother Jenny. Oliver and Jenny's current nanny declines to join them and the over-worked parents/executives must take care of their newborn baby Sarah in Puerto Rico. Amidst corporate scheming by the young company CFO Walter Hausen, who is planning a takeover of Oliver's company CCI Tekhausen (formed in Au Pair II), Oliver and Jenny must contend with bridging the generation gap with the family, new career motivations and the romances of their 'newly reformed' prankster kids.